/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.util;

import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThanOrEqualTo;
import static org.hamcrest.Matchers.lessThanOrEqualTo;
import static org.hamcrest.Matchers.sameInstance;

import java.util.Arrays;
import java.util.Random;
import org.apache.lucene.tests.util.LuceneTestCase;
import org.apache.lucene.tests.util.TestUtil;

public class TestRadixSelector extends LuceneTestCase {

  public void testSelect() {
    for (int iter = 0; iter < 100; ++iter) {
      doTestSelect();
    }
  }

  private void doTestSelect() {
    Random random = nonAssertingRandom(random());
    final int from = random.nextInt(5);
    final int to = from + TestUtil.nextInt(random, 1, 10000);
    final int maxLen = TestUtil.nextInt(random, 1, 12);

    BytesRef[] arr = new BytesRef[from + to + random.nextInt(5)];
    for (int i = 0; i < arr.length; ++i) {
      byte[] bytes = new byte[TestUtil.nextInt(random, 0, maxLen)];
      random.nextBytes(bytes);
      arr[i] = new BytesRef(bytes);
    }
    doTest(arr, from, to, maxLen);
  }

  public void testSharedPrefixes() {
    for (int iter = 0; iter < 100; ++iter) {
      doTestSharedPrefixes();
    }
  }

  private void doTestSharedPrefixes() {
    Random random = nonAssertingRandom(random());

    final int from = random.nextInt(5);
    final int to = from + TestUtil.nextInt(random, 1, 10000);
    final int maxLen = TestUtil.nextInt(random, 1, 12);
    BytesRef[] arr = new BytesRef[from + to + random.nextInt(5)];
    for (int i = 0; i < arr.length; ++i) {
      byte[] bytes = new byte[TestUtil.nextInt(random, 0, maxLen)];
      random.nextBytes(bytes);
      arr[i] = new BytesRef(bytes);
    }
    final int sharedPrefixLength = Math.min(arr[0].length, TestUtil.nextInt(random, 1, maxLen));
    for (int i = 1; i < arr.length; ++i) {
      System.arraycopy(
          arr[0].bytes,
          arr[0].offset,
          arr[i].bytes,
          arr[i].offset,
          Math.min(sharedPrefixLength, arr[i].length));
    }
    doTest(arr, from, to, maxLen);
  }

  private void doTest(BytesRef[] arr, int from, int to, int maxLen) {
    final int k = TestUtil.nextInt(random(), from, to - 1);

    BytesRef[] expected = arr.clone();
    Arrays.sort(expected, from, to);

    BytesRef[] actual = arr.clone();
    final int enforcedMaxLen = random().nextBoolean() ? maxLen : Integer.MAX_VALUE;
    RadixSelector selector =
        new RadixSelector(enforcedMaxLen) {

          @Override
          protected void swap(int i, int j) {
            ArrayUtil.swap(actual, i, j);
          }

          @Override
          protected int byteAt(int i, int k) {
            assertTrue(k < enforcedMaxLen);
            BytesRef b = actual[i];
            if (k >= b.length) {
              return -1;
            } else {
              return Byte.toUnsignedInt(b.bytes[b.offset + k]);
            }
          }
        };
    selector.select(from, to, k);

    assertThat(actual[k], equalTo(expected[k]));
    for (int i = 0; i < actual.length; ++i) {
      if (i < from || i >= to) {
        assertThat(actual[i], sameInstance(arr[i]));
      } else if (i <= k) {
        assertThat(actual[i], lessThanOrEqualTo(actual[k]));
      } else {
        assertThat(actual[i], greaterThanOrEqualTo(actual[k]));
      }
    }
  }
}
